Radar Apparatus and Method for Operating a Radar Apparatus

The present invention relates to a radar apparatus and to a method for operating a radar apparatus.

Radar measurement technology is used alongside other measurement principles to record the environment in automotive, industrial, or consumer applications. Radar sensors use electromagnetic waves propagating at the speed of light to perform measurements by measuring the time interval from a transmitted signal to a point of reflection and back, i.e., the echo arrival time. From this time of flight, the range and/or relative velocity of the reflection point with respect to the sensor can then be determined.

A common operating method for radar sensors is the FMCW (frequency-modulated continuous wave) method, in which a single carrier is linearly modulated in its frequency and transmitted. The echo reflected from the reflection points is then mixed with the modulated carrier in the receiver channels of the radar sensor, resulting in an intermediate frequency proportional to the radial distance of the reflection point. The intermediate frequency can be determined, for example, by a fast Fourier transform. To determine the radial velocity, a plurality of frequency-modulated carriers can be transmitted and received one after the other, the frequency shift of which over time corresponds to the Doppler frequency, from which the relative velocity can be calculated.

To determine the angle of the reflection point, a plurality of transmitter and receiver channels can be used within a single radar sensor.

TX TX By suitably designing the antenna system, a virtual array consisting of N. NRx channels can be formed, where Ndenotes the number of transmitters and NRx denotes the number of recipients. Based on the phase difference between the individual echoes, it is possible to determine azimuth angles and/or elevation angles. This method is called the MIMO (multiple-input multiple-output) radar method.

In addition, phased array antennas are used in communication and radar applications. By means of phase shifters and, where appropriate, adjustable amplifiers in the transmitter channels, they allow for adaptive steering of the main beam direction of a multichannel radar system. Thus, the otherwise predetermined main beam direction of the radar sensor can be changed during operation.

U.S. Pat. No. 11,360,210 B2 describes a MIMO radar sensor in which the transmitter can be reconfigured to switch between different fields of view of the sensor.

The frequency ramp required for the FMCW radar can be adjusted by means of a phase-locked loop (PLL), which changes the output frequency over time. Due to the ramp linearity required to achieve the required sensitivity for the radar system, the phase-locked loop is very demanding and complex. With continuing advances in integration, broadband digital-to-analog converters and DDS (direct signal synthesis) converters are now available, so that the ramp can also be implemented without a phase-locked loop.

In Germany Patent Application No. DE 10 2016 224 945 A1, different ramp generators are used for the transmitting path and the receiving path, with different carrier frequencies being used for the transmitter channels.

The present invention provides a radar apparatus and a method for operating a radar apparatus.

Preferred embodiments of the present invention are disclosed herein.

According to a first aspect, the present invention relates to a radar apparatus having a local oscillator which generates a local oscillator signal having a constant frequency. The radar apparatus also comprises at least one device which transmits radar signals and/or receives radar signals. The device has a ramp generator which, depending on the local oscillator signal, generates a ramp signal and distributes the signal within the device.

According to a second aspect, the present invention relates to a method for operating a radar apparatus. A local oscillator signal having a constant frequency is generated here. Radar signals are transmitted and received by means of at least one device, wherein the device has a ramp generator which, depending on the local oscillator signal, generates a ramp signal and distributes said signal within the device.

The radar apparatus of the present invention may be integrated as a highly integrated semiconductor circuit. Preferably, a plurality of devices can be interconnected (cascaded). This makes it possible to increase the number of implementable transmitter and receiver channels for coherent angle measurement in radar sensors, which is particularly advantageous for high-performance FMCW radar sensors, which are also suitable, for example, for automotive applications in the area of increasing highly automated driving functions.

The local oscillator itself generates a signal having a constant frequency, which can more easily be distributed to the individual devices than an already modulated signal. The devices each have a ramp generator, so that the signal is modeled (i.e., the ramp is generated) separately in each device.

The radar apparatus may be designed as an FMCW radar apparatus without the need for a phase-locked loop for ramp generation. The local oscillator only needs to provide the local oscillator signal having a constant frequency, i.e., a fixed-frequency carrier, so that design parameters such as phase noise can be specifically optimized for this application. At the same time, the advantages of a conventional FMCW radar apparatus are retained, such as a narrow reception bandwidth and the proportionality between baseband frequency and the target's radial range in the measured scene (and thus the ability to perform range compression and to limit the measurement range by low-pass filtering). By using phase shifters and configurable amplifiers, conventional modulation concepts such as the separation of transmitter channels by phase change in code/Doppler methods or phased arrays can be realized.

The fixed-frequency local oscillator signal also allows for simplified cascading of a plurality of devices designed as integrated circuits in order to increase the number of transmitter or receiver channels of the radar apparatus.

According to one example embodiment of the radar apparatus of the present invention, the at least one device is a function block which comprises transmitting paths and/or receiving paths. A device may be implemented as an integrated semiconductor circuit.

According to one example embodiment of the radar apparatus of the present invention, there are a plurality of devices, which devices can be parameterized independently of one another, so that adaptively configurable multimode radar apparatuses can be realized.

According to one example embodiment of the present invention, the radar apparatus has a reference oscillator which is designed to generate a reference signal, wherein the local oscillator is designed to generate the local oscillator signal using the reference signal.

According to one example embodiment of the present invention, the radar apparatus has a clock generator which is designed to, depending on the reference signal, generate a clock signal and to output said clock signal to the at least one device. In addition to the local oscillator signal, the clock signal provides another signal which is also derived from the reference signal.

According to one example embodiment of the radar apparatus of the present invention, the ramp generator has at least one IQ mixer, wherein the local oscillator is designed to output the local oscillator signal to the IQ mixer. The IQ mixer is used to generate the ramp signal.

According to one example embodiment of the radar apparatus of the present invention, the ramp generator has at least two direct digital synthesis (DDS) devices. The at least two DDS devices control the IQ mixer. The DDS devices can be used for modulation. In particular, the ramp generator may have a first DDS device and a second DDS device. The first DDS device controls an I path of the IQ mixer. The second DDS device controls a Q path of the IQ mixer.

According to one example embodiment of the radar apparatus of the present invention, the at least one DDS device is designed to, depending on the clock signal generated by the clock generator, control the IQ mixer.

According to one example embodiment of the radar apparatus of the present invention, the ramp generator has a first digital-to-analog converter and a second digital-to-analog converter. The first digital-to-analog converter controls an I path of the IQ mixer. The second digital-to-analog converter controls a Q path of the IQ mixer.

According to one example embodiment of the radar apparatus of the present invention, the first digital-to-analog converter is designed to, depending on the clock signal generated by the clock generator, control the I-path of the IQ mixer. The second digital-to-analog converter is designed to, depending on the clock signal generated by the clock generator, control the Q path of the IQ mixer.

According to one example embodiment of the radar apparatus of the present invention, the local oscillator can change the frequency of the local oscillator signal stepwise. However, the local oscillator signal does not need to be modulated (e.g., it is not ramp-shaped).

According to one example embodiment of the radar apparatus of the present invention, there are a plurality of devices, and each device is formed on a separate semiconductor chip.

According to one example embodiment of the radar apparatus of the present invention, there are a plurality of devices, and distribution of the local oscillator signal from the local oscillator to the devices is asymmetrical. The ramp generators of the devices are designed to compensate for the asymmetric distribution of the local oscillator signal. For example, all devices transmit the same frequency ramp, wherein the distribution of the local oscillator signal is asymmetrical, for example by means of an asymmetric star or by means of a ring. The line geometries of the distribution of the local oscillator signal are known from the sensor design, which is why compensation is possible by changing the start time or start phase of the ramp generator, so that the desired signal is obtained after the mixing process. Calibration is possible, for example, during end-of-line antenna calibration.

According to one example embodiment of the radar apparatus of the present invention, when the local oscillator signal is distributed symmetrically among the devices, all of the devices of the radar apparatus use the same ramp configuration, including, for example, ramp start times, a start frequency, an end frequency, a ramp slope and/or a start phase.

According to one example embodiment of the radar apparatus of the present invention, at least two devices, and preferably a plurality of devices, are used, which are divided into at least two subsystems. Thus, a multimode radar apparatus is provided in which different modulations may be used in the subsystems. These are synchronized with one another in such a way that mutual interference is avoided. When using a suitable antenna system, scene-adaptive redistribution of existing channels is also possible. For example, a radar beam may be emitted constantly along the central axis (boresight) and at least one additional flexible radar beam may be provided.

According to one example embodiment of the radar apparatus of the present invention, there is only one device which has both transmitter channels and receiver channels. If this device is integrated together with a local oscillator and/or a reference oscillator as a semiconductor circuit, a complete FMCW radar system may be provided.

Further advantages, features, and details of the present invention will become apparent from the following description, in which various exemplary embodiments of the present invention are described in detail with reference to the figures.

In all figures, identical or functionally identical elements and apparatuses are provided with the same reference signs. The numbering of method steps serves the purpose of clarity and is generally not intended to imply a specific chronological order. In particular, a plurality of method steps may also be carried out simultaneously.

1 FIG. 100 1 shows a radar apparatushaving a reference oscillatorwhich generates a reference signal. The reference oscillator may, for example, be a quartz oscillator.

100 2 The radar apparatusfurther comprises a local oscillatorwhich, using the reference signal, generates a local oscillator signal having a constant frequency. The local oscillator is a high-frequency source, e.g., based on a phase-locked loop, which operates, for example, in the range of 19 to 20.25 GHZ.

2 1 According to some embodiments, the local oscillator signal provided by the local oscillatorbased on the reference signal of the reference oscillatormay be divided into time segments, each having a different frequency that is constant within the time segment.

50 a The radar apparatus also comprises at least one, and preferably a plurality of, devices, i.e., TX/RX blocks (transmitter/receiver blocks), which have transmitting devices for generating and transmitting radar signals and/or receiving devices for receiving radar signals.

50 50 50 50 50 a a a a a Arbitrary combinations are possible. That is, some devicesmay be designed only to generate and transmit radar signals, some devicesmay be designed only to receive radar signals, and some devicesmay be designed both to generate and transmit radar signals and to receive radar signals. An arbitrary combination of such devicesis possible. Each devicemay be formed on a separate chip.

2 50 50 4 a a 1 FIG. The local oscillator signal of the local oscillatoris distributed to all devices. This can be done symmetrically or asymmetrically.illustrates one of the devicesby way of example. The local oscillator signal is distributed via linesto further devices that are not shown.

50 5 6 a The deviceoptionally has a frequency multiplierwhich multiplies the local oscillator signal by a multiplication factor M≥1, in particular M≥1, to the desired input frequency of a ramp generator.

6 50 50 50 6 a a a The ramp generatorgenerates, depending the (optionally multiplied) local oscillator signal, a ramp signal, such as a chirp sequence, and distributes the ramp signal within the device. “Distributing” means that the ramp signal is output to a plurality of components of the device(e.g., transmitter channels and/or receiver channels). Accordingly, each devicecomprises its own ramp generatorfor applying modulation to the local oscillator signal.

6 7 6 8 The ramp generatorcomprises a splitterwhich splits the incoming signal into a signal in an I path and a signal in a Q path, which are shifted by 90 degrees in phase with each other. The ramp generatoralso comprises an IQ mixerwhich mixes the IQ signal with further provided signals, described below, and thereby generates the ramp signal.

100 3 The radar apparatuscomprises a clock generatorwhich, depending on the reference signal, generates and outputs a clock signal (e.g., a system clock). The clock signal may be independent of the local oscillator signal, i.e., in particular said clock signal may have an independent frequency.

30 13 15 28 9 10 11 The reference signal is provided to a processing device, a first direct digital synthesis (DDS) deviceor a second DDS deviceand an analog-to-digital convertervia optional frequency dividers,,(with division factors R, S and T). Because all signals are derived from the clock signal, they are phase-locked to one another.

13 15 12 14 8 8 The first DDS deviceand the second DDS devicegenerate signals which are filtered with low-pass filtersand, respectively, and mixed with the signal in the I path of the IQ mixerand with the signal in the Q path of the IQ mixer, respectively.

13 15 13 15 In further embodiments, instead of the first DDS deviceand the second DDS device, a first digital-to-analog converterand a second digital-to-analog converterare used.

13 15 8 In further embodiments, radio frequency digital-to-analog converters (RF DACs) are used instead of the first DDS deviceand the second DDS device, whereby the IQ mixercan be omitted.

100 16 6 19 29 Furthermore, the radar apparatuscomprises an optional frequency multiplierhaving a multiplication factor N≥1, in particular where N≥1. For example, if the ramp generatordoes not operate in the target frequency band, such as 76 to 81 GHZ for an automotive radar apparatus, the output signal is, before distribution to transmitter and/or receiver channels,, multiplied by the multiplication factor N into the target frequency band.

12 14 13 15 By means of the low-pass filters,, it can be ensured that the by the first DDS deviceand the second DDS deviceand, respectively, by the first digital-to-analog are adequately suppressed. Typical values for the sum of M and N are:

50 21 19 29 a The modulated local oscillator signal in the target frequency band (i.e., the ramp signal) is then distributed within the devicevia linesto the transmitter and/or receiver channels,.

19 18 17 19 19 50 20 a A transmitter channelcomprises a power amplifierand a phase shifter, with which the transmitter channelcan be switched on, an output power can be adjusted, and, optionally, a relative phase of different transmitter channelsof the devicecan be adjusted. The signal is transmitted via antennas.

100 The radar apparatusmay be operated using code or Doppler-based multiplexing methods. Furthermore, phased arrays may be realized, wherein a plurality of transmitter channels allow the main beam direction to be controlled or the side lobes to be suppressed.

29 22 23 24 6 16 In the receiver channels, the signal is received via antennas, optionally amplified by means of an amplifierand fed to a receiving mixer, which mixes the received signal with the output signal of the ramp generator, which output signal was optionally multiplied by the frequency multiplier.

50 6 24 29 a Because each devicehas a ramp generator, it is possible to downmix the linear frequency-modulated transmission signal within the receiving mixers, as in conventional radar systems, using a frequency ramp with identical parameterization, thereby retaining the advantage of decoupling the radio frequency bandwidth from the baseband bandwidth. Accordingly, the configuration of the receiver channelsmay substantially correspond to a conventional FMCW receiving path and may be implemented as narrowband on the baseband side, e.g., with a bandwidth in the range of 10 to 100 MHZ.

25 27 25 27 26 28 30 In addition, the proportionality of the baseband frequency and radial distance of each target is still maintained, so that high-pass filtering by a high-pass filterand low-pass filtering by a low-pass filterof the baseband signals for dynamic range limitation or for suppressing targets with a distance outside the parameterized measuring range is also possible. Between the high-pass filterand the low-pass filter, the signal can be amplified by another amplifier. The signal is finally sampled by an analog-to-digital converterand fed to the processing device.

30 31 Furthermore, synchronization or data exchange of the processing devicewith other components may take place via interfaces.

2 FIG. 1 FIG. 200 100 200 3 2 9 10 11 50 50 50 b b b shows a further radar apparatus. This radar apparatus differs from the radar apparatusshown inin that the radar apparatusdoes not have a clock generator. Rather, the local oscillator signal from the local oscillatoris fed to the frequency dividers,,and to the respective downstream components. This reduces the distribution effort for cascaded devices. In particular, only one signal needs to be distributed to the individual devices. In addition, the individual clock pulses are phase-locked not only to one another but also to the local oscillator signal. Optionally, each devicemay also have a phase-locked loop which, based on the variable local oscillator signal, generates a fixed-frequency system clock pulse.

3 3 FIGS.A andB 300 300 50 50 19 19 29 29 c d a b a b. together show a further radar apparatus. This is a cascaded radar apparatushaving two devices,having separate transmitting devices,and receiving devices,

300 50 50 32 c d Depending on the number of channels of the radar apparatusand the higher-level system concept, the processing of the radar data may be carried out either within the devices,or in a separate apparatus.

50 50 5 5 6 6 7 7 8 8 12 12 14 14 13 13 15 15 50 50 30 30 16 16 21 21 c d a b a b a b a b a b a b a b a b c d a b a b a b The devices,each comprise optional frequency multipliers,and their own ramp generators,having the components described above, i.e., splitters,, IQ mixers,, low-pass filters,,,, a first DDS device,(or first digital-to-analog converter) and a second DDS device,(or second digital-to-analog converter). Furthermore, the devices,each comprise a processing device,and an optional frequency multiplier,, as well as lines,to transmitting and receiving paths, respectively.

50 19 19 18 18 1717 17 20 20 c a b a b a b a b. The devicecomprises first and second transmitter channels,, each having a power amplifier,and a phase shifter,, as well as antennas,

50 29 29 23 23 24 24 25 25 26 26 27 27 28 28 d a b a b a b a b a b a b a b. The devicecomprises first and second receiver channels,, each having an amplifier,, a receiving mixer,, a high-pass filter,, an amplifier,, a low-pass filter,, and an analog-to-digital converter,

50 50 6 6 50 50 c d a b c d Furthermore, a synchronization interface may be provided between the devices,, which allows for deterministic start times for the respective ramp generators,. A data interface allows for the exchange or forwarding of optionally pre-processed received signals to downstream processors. The devicesandcan also be configured via corresponding interfaces.

50 50 6 a d Independently of the embodiment, it is no longer necessary to distribute the modulated local oscillator signal between the individual devices-(e.g., on a printed circuit board), but only a (at least stepwise) fixed-frequency local oscillator signal. This significantly simplifies distribution, in particular for sensors having a plurality of channels, because length differences in the local oscillator signal distribution and any resulting phase drift can be compensated for by re-parameterizing the ramp generators, i.e., their start phase and time.

6 6 6 50 50 a b a d Distribution of the local oscillator signal from the local oscillator to the devices may also be asymmetrical. The ramp generators,,of the devices-are then designed to compensate for the asymmetric distribution of the local oscillator signal.

4 FIG. 100 200 300 shows a flow chart of a method for operating a radar apparatus, in particular one of the radar apparatuses,,described above.

2 In a first step S1, a local oscillator signal having a constant frequency is generated. For this purpose, a local oscillatoras described above can be provided.

50 50 50 50 6 6 a d a d a d In a second step S2, radar signals are transmitted and received by means of at least one and preferably a plurality of devices-, wherein each device-has a ramp generator-which, depending on the local oscillator signal, generates a ramp signal.

1 2 Furthermore, a reference oscillatormay be provided which generates a reference signal, wherein the local oscillatorgenerates the local oscillator signal using the reference signal.

3 50 50 a d. A clock generatormay optionally be provided which is designed to, depending on the reference signal, generate a clock signal and to output said clock signal to the devices-

6 6 6 8 8 8 2 8 8 8 a b a b a b. The ramp generators,,may each have an IQ mixer,,, wherein the local oscillatoroutputs the local oscillator signal to the IQ mixer,,

6 6 6 13 15 13 15 13 15 a b a a b b. The ramp generators,,may each have at least one DDS device or at least one analog-to-digital converter,,,,,

2 The local oscillatormay also be designed to change the frequency of the local oscillator signal stepwise.

50 50 2 50 50 6 6 6 50 50 a d a d a b a d Each device-may be formed on a separate chip. Distribution of the local oscillator signal from the local oscillatorto the devices-may also be asymmetrical, wherein the ramp generators,,of the devices-compensate for the asymmetric distribution of the local oscillator signal.